[Radiance-general] mkillum illuminating outside?

[Greg Ward]

Hi Lars,

Nice that I slept through this one, too...  Your debugging tips are  
helpful.  Another way to determine whether you are looking at the  
back or front of a surface is in rvu, which reports the first surface  
hit (even if it's invisible) and tells you back or front.  This is  
only for materials that care which side you hit, like lights, illums,  
dielectric, etc.  Plastic and metal won't let you know.  The only way  
to tell for these surfaces is to turn backface visibility off with - 
bv0.  This can cause your scene to look a bit confused, so I only  
recommend it as a last resort.

Best,
-Greg

> From: "Lars O. Grobe" <akilog at nus.edu.sg>
> Date: February 11, 2009 3:30:18 AM PST
>
> Sorry, this was a stupid mistake of mine. When I replaced the  
> polygon surface that I had been using before by a !gensurf-line, I  
> ended up with a wrong surface normal. This made my illum become  
> oriented to the outside world. As the other surfaces where still  
> facing inwards, the culprit surface still got enough light from the  
> sides to illuminate the opposite wall. I only found this when I  
> switched to the light modifier type using mkillums l+, because than  
> the surface appeared completely black when seen from inside (the  
> illum being not visible itself makes this kind of debugging more  
> difficult, and I was 100% sure that the orientation was ok because  
> I had tested it before - but than there had been the polygon).
>
> So, this is my second non-problem reported to the list, sorry for  
> messing up your mail boxes...
>
> CU Lars.